Not issued in numerical or chronological order: Vol. 22, pt. 1 published May 22, 1905
"It was planned to complete the Flora in 34 volumes. Some 94 parts of 24 volumes were published at irregular intervals between 1905 and 1949 ... The project to complete the 34 volumes was discontinued. Therefore, no further parts will be assigned to the 34 volume series. Instead, North American flora series II, initiated in 1954, is being published ..."--North American flora. Series II, pt. 13 (14 Nov. 1990)
Vols. 4, 5, 8, 12, 13, 20, 26, 27, 30 and 31 never published; only vols. 7, 8 and 28B were completed